Lines and wrinkles on the skin are caused by degenerative changes in the proteins of the dermal extracellular matrix. They are signs of both chronologically-aged and photo-aged skin. In the past years, chronological aging and photo-aging were classified as different phenomena. However, in recent years, researchers have discovered some common molecular mechanisms between the two. Such mechanisms include decreased synthesis of new collagen, decreased anti-oxidative activities, and increased amount of matrix metalloproteases (MMPs).
MMPs are members of the zinc-dependent endopeptidases family. To date, there are over twenty known MMPs, each labeled in a general format “MMP-x,” wherein x≧1. The MMP gene family can be divided according to their substrate specificity and structure into subgroups of collagenases, gelatinases, stromelysins, matrilysin, enamelysin, membrane-type MMP, and others. For example, MMP-1 is a collagenase, MMP-3 is a stromelysin, and MMP-9 is a gelatinase.
One major biological function of MMPs is to catalyze the breakdown of macromolecules in the extracellular matrix such as collagen and elastin. The breakdown of dermal collagen and elastin is purported to be one of the major contributing factors to loss of skin's firmness and elasticity. Such changes cause the skin to appear aged (i.e., dull, wrinkled, and saggy). Thus, it is of great importance to reduce, if not completely block, the enzymatic activity of MMPs.
In fact, human tissues are capable of naturally producing inhibitors of MMPs known as tissue inhibitors of matrix metalloproteases (TIMPs). At present, the TIMP gene family consists of four members: TIMP-1, TIMP-2, TIMP-3, and TIMP-4. TIMPs are capable of reversibly inhibiting the MMPs in a 1:1 stoichiometric fashion. A more detailed and comprehensive review of MMPs and TIMPs has been presented by Woessner and Nagase in Matrix Metalloproteinases and TIMPs, Oxford University Press, 2000. In addition to their inhibitory role against MMPs, TIMPs are also able to promote cell proliferation in a wide range of cell types and may have an anti-apoptotic function. This indicates that TIMPs may be able to serve as MMP inhibitors as well as skin regenerators. Unfortunately, the biological production of TIMPs decreases with aging, while the production of MMP increases, thereby contributing to the aging of the skin. Thus, it is desirable to supplement the depleted TIMPs by delivering to the skin inhibitors of MMP.
To date, a number of agents have been studied for their potency as MMP inhibitors. For example, it has been demonstrated that the topical application of epigallocatechin-3-gallate or retinoic acid to a skin tissue model prior to UVA irradiation prevents an increase in MMP-1 (interstitial collagenase) expression and activity. (Jong Hee Lee, et al., The Effects of Epigallocatechin-3-gallate on Extracellular Matrix Metabolism, Journal of Dermatological Science, 40(3); 195-204 (December 2005)). Similarly, 2′,4′,7-trihydroxyisoflavone, also prevents increases in UV-induced MMP-1 activity in cultured fibroblasts. Other examples of MMP inhibitors are described and studied as CT1166 and RO31-7467 by Hill et al. (Peter A. Hill, et al., Inhibition of Bone Resorption In Vitro by Selective Inhibitors of Gelatinase and Collaginase, Biochemical Journal, 308; 167-175 (1995)).
Of the MMP inhibitors studied, some are used in topical cosmetic compositions to counteract the effect of photo- and chronological skin aging. For example, certain di-peptide analogs with fused or conjugated bicycloaryl substitutes are potent broad-spectrum hydroxamate inhibitors of MMPs. One example of such di-peptides is Galardin (INCI name: N-[(2R)-2-(hydroxamidocarbonylmethyl)-4-methylpentanoyl]-L-tryptophan methylamide), the structure of which is shown below:

Galardin inhibits MMP activities by interacting with the zinc atom in the active site of MMPs. Another example of commercially available MMP inhibitor is Pepha®-TIMP available from Pentapharm AG. Pepha®-TIMP is TIMP-2 which exhibits strong inhibitory effect towards MMP-1, but also effective against MMP-2, MMP-3, MMP-8, and MMP-9.
Furthermore, the use of MMP inhibitors in combination with other anti-aging cosmetic agents is known in the art. For example, the use of UV blockers (e.g. octinoxate and zinc oxide) in combination with an MMP inhibitor for inhibiting photoaging of skin is known. Cosmetic compositions including an MMP inhibitor and a natural estrogen (e.g., 17-beta estradiol or an estrogen-like steroid) have also been reported to diminish skin wrinkles and fine lines.
Another example of agents known to be combined with MMP inhibitors is antioxidants. Antioxidants are molecules or complexes that are capable of slowing or preventing the oxidation of other biomolecules caused by free radicals and reactive oxygen species. Damages to healthy cells caused by such harmful agents are a major contributor to wrinkles and precancerous cell changes in the skin. In fact, human body is capable of producing natural antioxidants. One example is superoxide dismutase (“SOD”), an enzyme that neutralizes superoxide free radical (.O2−), which is the most common free radical in the body that can damage other important enzymes, membrane lipids, and nucleic acids. Additionally, SOD promotes cell repair and production of functional fibroblasts in the dermis. However, the SOD levels decrease with age. Thus, much of dermapharmaceutical compositions known in the art have been combining MMP inhibitors and antioxidants in an effort to replenish the body's deficiency of such anti-aging agents.
However, a common shortcoming of aforementioned cosmetic compositions comprising MMP inhibitors and anti-aging agents is that they provide short-term MMP inhibitory and antioxidative activities. Such compositions temporarily reverse or reduce the skin damage caused by MMPs, but they must be frequently reapplied to the skin for a lasting anti-aging effect. This is impractical and uneconomical from the consumers' perspective. Thus, researchers are now looking to agents with long-term anti-aging effect that stimulate the body's production of endogenous MMP inhibitors (i.e., TIMPs) and/or SOD.
The up-regulation of TIMP gene in the skin is considered as a form of long-term “anti-aging” mechanism, because an increase in the number of TIMPs contributes to the reduction of MMPs' destructive activities. The human body is capable of up-regulating the expression of TIMP genes by various cytokines. For example, the production of TIMP-1 and TIMP-3 are enhanced by a cytokine called Transforming Growth Factor beta (TGF-β). (Laura Mattila et al., Activation of Tissue Inhibitor of Metalloproteinases-3 (TIMP-3) mRNA Expression in Scleroderma Skin Fibroblasts, The Journal of Investigative Dermatology, 110(4); 416-421 (April 1998); and Kanako Kikuchi et al., Tissue Inhibitor of Metalloproteinase 1 (TIMP-1) May be an Autocrine Growth Factor in Scleroderma Fibroblasts, The Journal of Investigative Dermatology, 108(3); 281-284 (March 1997)). TIMP-2 has been shown to be induced by another type of cytokine called interleukin-4 (IL-4). (Ihn et al., IL-4 Up-Regulates the Expression of Tissue Inhibitor of Metalloproteinase-2 in Dermal Fibroblasts via the p38 Mitogen-Activated Protein Kinase-Dependent Pathway, The Journal of Immunology, 168; 1895-1902 (February 2002)). However, products providing such long-term effects alone are inadequate to attract consumers who are interested to see immediate results.
Thus, it is desirable to provide a topical composition that provides a long-term anti-aging benefits to the skin comprising an agent that induces TIMP production (“TIMP inducing agent”) and an agent that induces SOD production (“SOD inducing agent”). There is also a need for a topical composition that further provides short-term anti-aging benefits to the skin comprising an MMP inhibitor. Similarly, there is a need for topical composition that incorporates SOD inducing agents and antioxidants for both a long-term and short-term protection from free radical damage to the skin. During our endeavor to create an effective anti-aging composition having long-term and short-term anti-aging effects, it has been unexpectedly discovered that the combination of an MMP inhibitor(s), a TIMP inducing agent(s), an antioxidant(s), and an SOD inducing agent(s) provides a remarkably synergistic antioxidative and MMP inhibitory activity, thereby providing powerful anti-aging effects on the skin.